feat: 会员中心全局暗色主题重构

阶段一：全局覆盖
- 新增 dark-override.css (450+ 行)，覆盖所有 Element UI 组件暗色样式
  - 输入框、表格、Tabs、弹窗、按钮、分页、复选框、下拉框等
  - 侧边栏、顶栏、主内容区暗色背景
  - 滚动条、日期选择器、消息面板等
- header.php 引入 dark-override.css

阶段二：页面独立 CSS 暗色化（22 个文件）
- 白色背景 #fff → #161b22
- 浅灰背景 #F3F5F9 → #0d1117
- 深色文字 #171725/#1E2736 → #E6E8EB
- 灰色文字 #8692B0 → #8B949E
- 浅色边框 #E6E7EB → rgba(255,255,255,0.06)
- 悬停背景 #F5F7FA → #21262d

clientarea/hgcloud/css/promotionDetail.css

@@ -7,7 +7,7 @@
   font-family: PingFang SC;
   font-weight: 400;
   line-height: 0.25rem;
-  color: #171725;
+  color: #E6E8EB;
 }
 .promotionDetail-contetn header img {
   display: block;
@@ -26,7 +26,7 @@
   font-family: PingFang SC;
   font-weight: 500;
   line-height: 0.25rem;
-  color: #1e2736;
+  color: #E6E8EB;
 }
 .promotionDetail-contetn main .el-form {
   padding-left: 0.5rem;
@@ -38,7 +38,7 @@
   font-size: 0.16rem;
   font-family: PingFang SC;
   font-weight: 400;
-  color: #1e2736;
+  color: #E6E8EB;
 }
 .promotionDetail-contetn main .el-form .el-form-item .el-form-item__content {
   width: 4rem;
@@ -56,9 +56,9 @@
   font-family: PingFang SC;
   font-weight: 400;
   line-height: 0.24rem;
-  color: #8692b0;
+  color: #8B949E;
 }
 .promotionDetail-contetn main .content-table {
-  border: 1px solid #e6e7eb;
+  border: 1px solid rgba(255,255,255,0.06);
   border-radius: 3px;
 }